ABSTRACT: PROJECT 5 Hazardous waste sites contain complex mixtures of a wide variety of toxic chemicals that contaminate and linger in the environment. The acute toxicities of numerous Superfund (SF) chemicals have been extensively investigated; however, further studies are needed to determine their chronic effects on human health. Several SF chemicals (e.g. naphthalene, PCBs, and CCl4), which are found in environmental samples from the Yurok Tribe of the Klamath River basin, and in California air, have been shown to induce endoplasmic reticulum (ER) stress in cultured cells. Furthermore, in animal models, long-term exposure to CCl4 leads to ER stress in tissues, resulting in fibrosis and organ damage. Thus, the central hypothesis for this project is that chronic exposure to xenobiotics leads to ER stress that then contributes to chronic inflammation, tissue fibrosis and eventual organ failure. Based on the novel concept that the magnitude of ER stress is proportional to the amount of chronic exposure to chemicals, and monitoring ER stress will help predict resulting biological effects, the long term goal of this project is to develop a high-content and medium throughput bioassay to test the potential of SF chemicals to induce ER stress (Aim IIIA), and a biomarker of ER stress-associated biological effects for bio-fluid analysis (Aim IIIB). Toward these objectives, cell-based assays (Aim I) will be used to understand the mechanisms by which exposure to environmental toxins leads to ER stress. In addition, in animal models (Aim II, with Project 4), Project 5 will evaluate the effects of chronic exposure to hazardous chemicals on ER stress, and test if seric oxylipids are surrogate biomarkers for ER stress (with Cores A and B). The methodology developed and data obtained from the cell cultures and animal models will be directly translated in developing biomarker assays (Aim IIIA and B; with Projects 2 and 3, and Cores A and B). Finally, research findings will be utilized to serve the community at large by testing field samples collected from the Klamath River basin, the Central Valley and the Sierra Nevada foothills in California, and at or around SF-sites across the U.S. (Aim IIIC with Project 1, Cores B, C and D), as well as transferring to the scientists of the Yurok Tribe Environmental Program (with Core E). Accordingly, the overall goals of this project are to: 1) test lipid mediators as potential diagnostic biomarkers for the magnitude of ER stress response that often contributes to organ damage, 2) develop fast, inexpensive and reliable new cell-based bioassays to detect, assess and quantitate the effects of hazardous substances on ER stress, 3) provide new mechanistic insights into the effects of chronic exposure to SF chemicals on ER stress and fibrotic diseases, 4) develop biomarkers assays for bio-fluids for the quantification of tissue-specific effects of xenobiotics on ER stress, and 5) translate our findings by assessing risk on human health, by analyzing field samples.